Our beloved D.C. United may have crashed and burned (again) in the MLS playoffs this season, but life goes on. Also, the playoffs go on — right in our backyard, in fact. Many moons ago, Washington was picked to host the 2007 MLS Cup this Sunday at noon, at RFK. Time to put aside your grieving and check out the game. Tickets start at $30, maybe even less on Craigslist. When else are you going…